Regeneration Responses to Management for Old-Growth Characteristics in Northern Hardwood-Conifer Forests

Abstract

Successful tree regeneration is essential for sustainable forest management, yet it can be limited by the interaction of harvesting effects and multiple ecological drivers. In northern hardwood forests, for example, there is uncertainty whether low-intensity selection harvesting techniques will result in adequate and desirable regeneration. Our research is part of a long-term study that tests the hypothesis that a silvicultural approach called "structural complexity enhancement" (SCE) can accelerate the development of late-successional forest structure and functions. Our objective is to understand the regeneration dynamics following three uneven-aged forestry treatments with high levels of retention: single-tree selection, group selection, and SCE. Regeneration density and diversity can be limited by differing treatment effects on or interactions among light availability, competitive environment, substrate, and herbivory. To explore these relationships, manipulations and controls were replicated across 2 ha treatment units at two Vermont sites. Forest inventory data were collected pre-harvest and periodically over 13 years post-harvest. We used mixed effects models with repeated measures to evaluate the effect of treatment on seedling and sapling density and diversity (Shannon-Weiner H'). The treatments were all successful in recruiting a sapling class with significantly greater sapling densities compared to the controls. However, undesirable and prolific beech (Fagus americana) sprouting dominates some patches in the understory of all the treatments, creating a high degree of spatial variability in the competitive environment for regeneration. Multivariate analyses suggest that while treatment had a dominant effect, other factors were influential in driving regeneration responses. These results indicate variants of uneven-aged systems that retain or enhance elements of stand structural complexity-including old-growth characteristics-can generally foster abundant regeneration of important late successional tree species depending on site conditions, but they may require beech control where beech sprouting inhibits desired regeneration.

Intermediate‐severity wind disturbance in mature temperate forests: legacy structure, carbon storage, and stand dynamics

“…We collected these photos separately from survey plots to provide supplemental data on overstory canopy conditions, placing a digital camera on a self‐leveling tripod above understory vegetation. We processed photos using HemiView software (Version 2.1; Delta‐T Devices 2012, Burwell, Cambridgeshire, UK) after Gottesman and Keeton () to estimate proportion of visible sky (i.e., gap fraction) and leaf area index.…”

Enhanced carbon storage through management for old‐growth characteristics in northern hardwood‐conifer forests

“…However, in our study, the contrast with no management was lowest across all carbon pools under SCE (17.45% less than baseline for live tree C) as compared to the conventional treatments (42.81% less than baseline for live tree C). This finding suggests great potential for low-intensity silvicultural techniques favoring in situ carbon storage in the northern hardwood region, assuming regeneration and other management objectives are met (Gottesman and Keeton 2017), which of course will vary tremendously by site and ownership (Schwenk et al 2012). The utility of management for in situ C storage must, of course, be considered within the larger context of carbon forestry, which includes approaches emphasizing carbon storage in wood products (FAO 2016) and avoided emissions from substitution of wood products for more energy-intensive materials (Malmsheimer et al 2008).…”

“…However, in our study, the contrast with no management was lowest across all carbon pools under SCE (17.45% less than baseline for live tree C) as compared to the conventional treatments (42.81% less than baseline for live tree C). This finding suggests great potential for low‐intensity silvicultural techniques favoring in situ carbon storage in the northern hardwood region, assuming regeneration and other management objectives are met (Gottesman and Keeton ), which of course will vary tremendously by site and ownership (Schwenk et al. ).…”

Projected Future Distribution of Tsuga canadensis across Alternative Climate Scenarios in Maine, U.S

“…The management of Tsuga canadensis in particular, may include site preparation [30] and the removal of the pervasive competitor, Fagus grandifolia saplings, which are shade tolerant and also susceptible to beech bark disease [5]. Forest and natural resource managers have called for information on climate change effects that is easily accessible and easy to interpret and implement [14].…”

“…Foundational tree species that exhibit old-growth characteristics are of particular interest because of their high biomass and contributions to stand structure [5]. Tsuga canadensis is considered a foundational tree species as a late-successional conifer that shapes stand microclimate and influences community and ecosystem characteristics.…”